A body A of mass m is moving in a circular orbit of radius R about a planet. Another body B of mass m 2 collides with A with a velocity which is half v → 2 the instantaneous velocity v → of A. The collision is completely inelastic. Then, the combined body:

starts moving in an elliptical orbit around the planet

continues to move in a circular orbit

Escapes from the Planet's Gravitational field

Falls vertically downwards towards the planet

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A cricket ball is dropped from a building of height $30 m$ and the coefficient of restitution between the ground and ball is $0.5$ . The total distance covered by the ball before it comes to rest is

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Important Questions on Work, Energy and Power

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Physics>Mechanics>Work, Energy and Power>Collisions

A particle of mass m is projected with a speed u from the ground at an angle

θ = \frac{π}{3}

w.r.t. horizontal (x-axis). When it has reached its maximum height, it collides completely inelastically with another particle of the same mass and velocity

u \hat{i} .

The horizontal distance covered by the combined mass before reaching the ground is:

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Physics>Mechanics>Work, Energy and Power>Collisions

A body

A

of mass

m = 0.1 k g

has an initial velocity of

3 \hat{i} m s^{- 1}

. It collides elastically with another body

B

of the same mass which has an initial velocity of

5 \hat{j} m s^{- 1}

. After the collision,

A

moves with a velocity

\vec{v} = 4 (\hat{i} + \hat{j}) m s^{- 1}

. The energy of

B

after the collision is written as

\frac{x}{10} J

. The value of

x

HARD

Physics>Mechanics>Work, Energy and Power>Collisions

A particle of mass

m

is dropped from a height

h

above the ground. At the same time another particle of the same mass is thrown vertically upwards from the ground with a speed of

\sqrt{2 g h} .

If they collide head-on completely inelastically, the time taken for the combined mass to reach the ground, in units of

\sqrt{\frac{h}{g}}

is:

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Physics>Mechanics>Work, Energy and Power>Collisions

During inelastic collision between two objects, which of the following quantity always remains conserved?

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Physics>Mechanics>Work, Energy and Power>Collisions

Fill in the blank with the most appropriate option given below.

We should give everyone training in citizenship, but we have______this aspect till now.

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Physics>Mechanics>Work, Energy and Power>Collisions

Two particles of equal mass

m

have respective initial velocities

u \hat{i}

and

u (\frac{\hat{i} + \hat{j}}{2})

. They collide completely inelastically. The energy lost in the process is:

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Physics>Mechanics>Work, Energy and Power>Collisions

A block of mass

m

moving on a frictionless surface at speed

v

collides elastically with a block of same mass, initially at rest. Now the first block moves at an angle

θ

with its initial direction and has speed

v_{1}

. The speed of the second block after the collision is

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Physics>Mechanics>Work, Energy and Power>Collisions

Two bodies of the same mass are moving with the same speed, but in different directions in a plane. They have a completely inelastic collision and move together thereafter with a final speed which is half of their initial velocities of the two bodies (in degree) is -

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Physics>Mechanics>Work, Energy and Power>Collisions

On a frictionless surfaces, a block of mass

M

moving at speed

v

collides elastically with another block of same mass

M

which is initially at rest. After collision the first block moves at an angle

θ

to its initial direction and has a speed

\frac{v}{3}

. The second block's speed after the collision is:

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Physics>Mechanics>Work, Energy and Power>Collisions

A tennis ball is dropped on a horizontal smooth surface. It bounces back to its original position after hitting the surface. The force on the ball during the collision is proportional to the length of compression of the ball. Which one of the following sketches describes the variation of its kinetic energy

K

with

t

time most appropriately? The figures are only illustrative and not to the scale.

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Physics>Mechanics>Work, Energy and Power>Collisions

A block of mass

1.9 kg

is at rest at the edge of a table, of height 1 m. A bullet of mass

0.1 kg

collides with the block and sticks to it. If the velocity of the bullet is

20 m s^{- 1}

in the horizontal direction just before the collision then the kinetic energy just before the combined system strikes the floor, is [Take

g = 10 m s^{- 2}

. Assume there is no rotational motion and loss of energy after the collision is negligible.]

HARD

Physics>Mechanics>Work, Energy and Power>Collisions

A sphere of mass $m$ moving with velocity $v$ collides head-on another sphere of same mass which is at rest. The ratio of final velocity of the second sphere to the initial velocity of the first sphere is ( $e$ is the coefficient of restitution and collision is inelastic)

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Physics>Mechanics>Work, Energy and Power>Collisions

Particle

A

of mass

m_{1}

moving with velocity

(\sqrt{3} \hat{i} + \hat{j}) {ms}^{- 1}

collides with another particle

B

of mass

m_{2}

which is at rest initially. Let

{\vec{v}}_{1}

and

{\vec{v}}_{2}

be the velocities of particles

A

and

B

after collision respectively. If

m_{1} = 2 m_{2}

and after collision

{\vec{v}}_{1} - (\hat{i} + \sqrt{3} \hat{j}) {ms}^{- 1}

, the angle between

{\vec{v}}_{1}

and

{\vec{v}}_{2}

is :

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Physics>Mechanics>Work, Energy and Power>Collisions

A body A of mass

m

is moving in a circular orbit of radius

R

about a planet. Another body B of mass

\frac{m}{2}

collides with A with a velocity which is half

(\frac{\vec{v}}{2})

the instantaneous velocity

\vec{v}

of A. The collision is completely inelastic. Then, the combined body:

EASY

Physics>Mechanics>Work, Energy and Power>Collisions

Blocks of masses

m, 2 m, 4 m

and

8 m

are arranged in a line of a frictionless floor. Another block of mass

m

, moving with speed

υ

along the same line (see figure) collides with mass

m

in perfectly inelastic manner. All the subsequent collisions are also perfectly inelastic. By the time the last block of mass

8 m

starts moving the total energy loss is

p %

of the original energy. Value of

p

is close to:
Question Image

EASY

Physics>Mechanics>Work, Energy and Power>Collisions

A metal ball of mass

2 kg

moving with a speed of

10 m s^{- 1}

had a head-on collision with a stationary ball of mass

3 kg

. If after collision, both the balls move together, then the loss in kinetic energy due to collision is

MEDIUM

Physics>Mechanics>Work, Energy and Power>Collisions

Two balls

A

and

B

of masses

50 kg

and

20 kg

are moving in a straight line in the same direction at speed of

9 km h^{- 1}

and

18 km h^{- 1}

respectively. Ball

B

hits

A

and reverses its direction at a speed of

27 km h^{- 1} .

The speed of the ball

A

after the collision is

HARD

Physics>Mechanics>Work, Energy and Power>Collisions

A small particle of mass

m

moving inside a heavy, hollow and straight tube along the tube axis, undergoes elastic collision at two ends. The tube has no friction and it is closed at one end by a flat surface while the other end is fitted with a heavy movable flat piston as shown in figure. When the distance of the piston from closed end is

L = L_{0}

the particle speed is

v = v_{0} .

The piston is moved inward at a very low speed

V

such that

V ≪ \frac{d L}{L} v_{0},

where

d L

is the infinitesimal displacement of the piston. Which of the following statement(s) is/are correct?

Question Image

HARD

Physics>Mechanics>Work, Energy and Power>Collisions

A simple pendulum, made of a string of length

l

and

a

bob of mass

m,

is released from a small angle

θ_{0} .

It strikes a block of mass

M,

kept on horizontal surface at its lowest point of oscillations, elastically. It bounces back and goes up to an angle

θ_{1} .

Then

M

is given by:

MEDIUM

Physics>Mechanics>Work, Energy and Power>Collisions

A moving block having mass

m,

collides with another stationary block having mass

4 m .

The lighter block comes to rest after collision. When the initial velocity of the lighter block is

v,

then the value of coefficient of restitution

(e)

will be

A cricket ball is dropped from a building of height 30 m and the coefficient of restitution between the ground and ball is 0.5. The total distance covered by the ball before it comes to rest is

Important Questions on Work, Energy and Power

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A cricket ball is dropped from a building of height $30 m$ and the coefficient of restitution between the ground and ball is $0.5$ . The total distance covered by the ball before it comes to rest is